#include <iomanip>
#include <iostream>
using namespace std;

int main()
{
	double w = 0.0;
	double s = 0.0;
	cin >> w;
	if (w <= 1)
	{
		s = 1;
	}
	else
	{
		int t = w;
		s = t * 1.8;
	}
	cout << fixed << setprecision(2) << s;
	return 0;
}
